The present invention generally relates to a device to seal shafts or stems penetrating into pressurized vessels in order to activate valves or other mechanisms and where it is desirable to seal said shafts or stems, and the opening through which said shafts or stems pass, from hazardous fluids passing or being contained within said valves or vessels.
Seals for stems heretofore employed were metal or plastic bellows, or flexible diaphragms. While bellows, as shown in my U.S. Pat. No. 5,058,861, are prone to fatigue problems, have limited excursions, and are limited to low pressures, diaphragms, as shown in my U.S. Pat. No. 4,609,178 can only be used for reciprocating stem motion, have limited excursion capabilities, are very space demanding, and are limited to relatively low pressures. They also require high actuating forces for motivation, caused by the fluid pressure acting on such a relatively large diaphragm area. This is a major cost item.
The present invention overcomes such difficulties in that a flexible tube (typically made from a rubber compound) is employed, surrounding and sealing said stems or shafts. Such a tube can easily be stretched over 100% of its original length without loosing its elasticity (depending on the material used) and is practically insensitive to fluid pressure, since the tube can not collapse, being completely supported, at the inside, by the passing stem or shaft. There is only an insignificant increase in actuating force above that caused by the fluid pressure acting on the cross-sectional area of the stem itself.
The tube, besides being able to be stretched, can likewise be twisted around a shaft by more than 180 degrees thereby permitting rotary actuations.
Furthermore, my sealing device is very compact since it requires an opening within a valve or vessel that is only slightly larger than the shaft or stem itself. This is a major cost improvement over current, state of the art, devices.
Finally, the manner of sealing the upper and the lower terminal ends of my tubular seal avoids the entrapments of poisonous matter or of micro-organisms.